1. Field of the Invention
The present invention relates to a peptide nanofiber having conductivity formed from a peptide that has a nanofiber-forming ability or a derivative of the peptide, and a method of manufacturing the same.
2. Description of the Related Art
Technology development for producing semiconductor elements and large-scale integrated circuits (LSI) using “top down” type approaches in which a large substance is subjected to miniaturization to give nanometer scale by cutting have been hitherto carried out extensively. However, such techniques have their limits, i.e., microstructures of 20 nm or less can not be produced. Thus, in recent years, investigations on construction of regular fine structures utilizing self-assembly of molecules have rapidly progressed. Representative examples of mimicking models for the “bottom up” type approach utilizing such self-assembly include cells of organisms, and investigations on development of novel materials with biomolecules using this as a model system have attracted great attention. Advantages of making a material with a biomolecule such as a protein or a nucleic acid constituting a living body involve the manufacturing system without waste because the material can be constructed through a manner of self-assembly without imparting energy externally, and biodegradability of the substance per se, and the like. Thus, the material may be referred to as having least impact on the global environment and organisms. In particular, there exist 20 kinds of natural amino acids constituting proteins, and the formed structure as well as the function may vary diversely. Therefore, nanotechnologies utilizing proteins are believed to be important in various fields hereafter.
FIG. 1 shows a process of forming peptide bonds among amino acids to construct a chain structure, which forms a final tertiary structure spontaneously. As shown in FIG. 1, the protein that is a biopolymer has a chain structure (FIG. 1B) in which 20 kinds of amino acids (comparatively simple organic molecule) (FIG. 1A) are primarily bound by dehydrative condensation, and forms a complex tertiary structure (FIG. 1C) through folding thereof. Proteins are a substance which carries out a variety of functions in a living body, for example in human, approximately several tens of thousands kinds of proteins have been referred to be used. In addition, proteins have a comparatively regular secondary structure constructed by many residues on the sequence through a folding process. They have predominantly α-helical structures and β-sheet structures, including those in which almost tertiary structures are α-helical structures (α-proteins), those in which almost tertiary structures are β-sheet structures (β-proteins), mixtures of both of them (αβ-proteins) and the like. Accordingly, proteins have their inherent structure according to each amino acid sequence, and the tertiary structure determines the function of each protein.
In recent years, a phenomenon was found in which one or many kinds of proteins may denaturate from their original inherent structures to spontaneously aggregate into fibrous forms. Many of these are toxic in a living body, which are referred to as relating to diseases such as Alzheimer's disease, BSE (so called mad cow disease) and the like. Fibrous aggregates having a size in the level of nanometer formed by self-assembly of such a protein or a peptide are referred to as amyloid fiber. FIG. 2 is a schematic view illustrating the overview of formation of the amyloid fiber. In phenomena of aggregation of multiple proteins to give a fibrous form, parts forming the fiber take β-sheet structure in many cases. Even though they are proteins not originally having a β-sheet structure, the part involving in fiber formation takes a β-sheet structure. Consequently, as shown in FIG. 2A and FIG. 2B, it has been believed that a number of β-sheets are linked via a hydrogen bond between the molecules to form a fiber, thereby providing a characteristic structure in amyloid fibers. Amyloid fibers have been believed to take an extremely regular structure in a nanometer scale. However, despite of thus resulting expectation to technical or industrial utilization, such techniques have not been established yet under current circumstances.
Many of amyloid fibers that are generally formed are very stable, and are not disrupted even in a high temperature condition (approximately 100° C.). Such stability is believed to result from the hydrogen bond formed upon generation of fibrous form from the amyloid fiber, because the hydrogen bond is isolated from surrounding aqueous solution by aggregation of the fibers to give a state in which the hydrogen bond is hardly broken by a water molecule. Heretofore, investigations of amyloid fibers have been carried out in connection with diseases such as Alzheimer's disease and BSE. However, taking into account of technical aspects, the factor, i.e., a stable fibrous structure, is believed to be an important property when various processings are performed while keeping the fibrous shape. Also, amyloid fibers have a diameter of approximately several nanometers, and a length may reach to several hundred nanometers to several ten micrometers, as the case may be. Therefore, they can be utilized as a nanofiber. Additionally, for making nanofibers have a greater deal of utility value, the nanofiber may be endowed with any function.
As described hereinabove, nanofibers are believed to take a structure with β-sheets linked in conjunction, suggesting availability as ultra-precise structural materials controlled at the nanoscale level. Arrangement of functional molecules is enabled while controlling at the nano level, thereby capable of providing materials that contribute to important technologies in technical and industrial aspects.
Further, because the structure of the amyloid fiber that is one of nanofibers is very stable, a greater deal of utility value as a structural material is suggested. Also, because of its biodegradability, it can be a material that is favorable for the environment. Therefore, when functional nanofibers can be produced through imparting a function to such a nanofiber, applications thereof in various fields are expected. In trends of recent semiconductor process technologies viewed as one example of the field of their application, much smaller width of wiring between the functional elements in a semiconductor device has been demanded. Under such circumstances, techniques for wiring using a nanofiber have been also attracted attention. Hence, organic molecules and the like having conductivity have focused interest. Scheibel, T., Parthasarathy, R., Sawicki, G., Lin, X. M., Jaeger, H., Lindquist, S. L., Proc. Natl. Acad. Sci. USA, 100, 4527-4532 (2003) reports an example in which a conductive function was imparted using a pathogenic protein that forms amyloid fibers, followed by binding of gold particle to the formed fiber. In this report, a conductive function is imparted by substituting one residue in a giant pathogenic protein comprising 253 residues with Cys, binding a gold particle to the Cys, subjecting to silver plating, and then subjecting to gold plating.